A lithium ion battery characterized in that a porous elastomer made of non-metal material is provided among the positive and negative electrodes groups, or between the electrodes groups and the inner wall of the shell and the elastomer is in the shape of sheet or stick. The thickness of the elastomer is 0.5 mm-5.0 mm, and the porosity is 10%-80%. The said battery can avoid effectively the expansion of the shell during the cycle of charge and discharge, and can be processed conveniently, and the cyclic life and safety property of the battery can be improved effectively.